WGLSceneRenderer Class Reference

Render scenes to buffers. More...

#include <WGLSceneRenderer.hpp>

Inheritance diagram for WGLSceneRenderer:

Collaboration diagram for WGLSceneRenderer:

Public Member Functions
	WGLSceneRenderer ()
	Construct a new WGLSceneRenderer object. More...
void	drawToBuffer (const Scene &scene, char *data, int len, bool drawColor=true)
	Draw Scene to a given buffer. More...
void	drawScene (Scene const &scene, bool drawColor=true)
	Draw the scene. More...
void	setActive () const override
	Set the WebGL state needed for the shader. More...
void	resize () override
	Resize to the resolution set for rake state in WGLContext. More...

Detailed Description

Render scenes to buffers.

When you have a list of vertices where neighbors in the list are adjunct vertices of a polygon, then the triangle fan of that list covers areas inside the polygon with an odd amount of triangles and areas outside of the polygon with an even amount or none.

Because we draw multiple polygons on top of each other and we don't want to draw each polygon separately we need to extend this scheme.

We need to figure out which is the first visible polygon for an fragment. For that we initialize each fragment with an stencil value of 0b10 then each time when the first triangle of an polygon is drawn on that fragment (depth test succeeds) we decrement this value, for the first polygon it is than 0b01 (an odd count). Each additional triangle over that fragment will toggle this value between 0b10 and 0b01 (even/odd count). If an polygon has an even number of triangles at this fragment (the fragment is outside of the polygon), the value will be 0b10 when the next polygon starts, and there fore the same as the initialisation. If an polygon as an odd number of triangles at this fragment (the fragment is inside the polygon), the value will be 0b01 what means if we subtract 1 now the value is 0. We use this 0 to indicate that this fragment is inside the polygon above the current one.

After this first draw pass, every fragment which is inside of at leas 1 polygon has an stencil value of 0 or 1. All with an one are visible so we can just draw them (this will happen in draw pass 3), because the correct depth is stored in the depth buffer.

For the fragments with stencil 0 we only now the depth value of the polygon below them, so we just draw every polygon above the stored depth value, this way we will use the painter algorithm to only show the polygon direct above the stored one.

Constructor & Destructor Documentation

WGLSceneRenderer()

WGLSceneRenderer::WGLSceneRenderer

(

)

Construct a new WGLSceneRenderer object.

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Member Function Documentation

drawScene()

void WGLSceneRenderer::drawScene	(	Scene const &	scene,
		bool	drawColor = true
	)

Draw the scene.

Parameters

scene	Scene object to draw.
drawColor	Wether to draw in color or color codes. Defaults to color.

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drawToBuffer()

void WGLSceneRenderer::drawToBuffer	(	const Scene &	scene,
		char *	data,
		int	len,
		bool	drawColor = true
	)

Draw Scene to a given buffer.

Used for screenshots.

Parameters

scene	Scene to draw.
data	Prealoocated buffer to use.
len	Length of data.
drawColor	Wether to draw in color or color codes. Defaults to color.

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resize()

void WGLSceneRenderer::resize ( )

overridevirtual

Resize to the resolution set for rake state in WGLContext.

Implements WGLRenderer.

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setActive()

void WGLSceneRenderer::setActive ( ) const

overridevirtual

Set the WebGL state needed for the shader.

Implements WGLRenderer.

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The documentation for this class was generated from the following files:

• include/WGLSceneRenderer.hpp
• src/WGLSceneRenderer.cpp